The invention concerns a temperature sensor with measuring resistor comprising a substrate with an electrically insulating surface and a resistance layer situated thereon, wherein the measuring resistor is surrounded by a casing of temperature-stable plastic through which leads of the measuring resistor are passed.
From DT 25 27 739 B2, (U.S. Pat. No. 4,050,052) a procedure is known for producing an electrical measuring resistor for a resistance thermometer in which a platinum thin film with a predetermined temperature coefficient is applied on a carrier of ceramic material, and the measuring resistor is subsequently provided with a temperature-stable cover layer, for example of epoxide resin, in order to be resistant to thermal and mechanical stresses. Moreover, the cover layer should offer protection against diffusion from the gas phase, solid substances from the surroundings, or against objects coming into contact with the measuring resistor.
Furthermore, from German utility model 89 13 803.1 a resistance thermometer is known for measuring surface temperature in which a metal layer temperature sensor is surrounded by a plastic casing through Which the leads of the resistance thermometer are passed to the outside. The plastic casing is manufactured in a multiple plastic extrusion die and is made of epoxide resin. The temperature sensor is provided for direct mounting on a surface whose temperature is to be measured.
Moreover, from DE 41 04 674 A1 a temperature sensor is known in which the measuring resistor serving as a sensor is formed by a platinum thin layer resistor on the front side of a plate-shaped carrier made of ceramic. This is enclosed in a basically pressure-tight tube-shaped glass housing, where it lies essentially free of tension only on its longitudinal edges, while all remaining smooth surfaces and edge surfaces, just like the measuring resistor itself are arranged completely contact-free in relation to the housing. In this way, the carrier can be enclosed vibration-free without there resulting an appreciable worsening of response behavior. Because of the relatively exact centering or precise alignment of the carrier in relation to the housing, manufacture is comparatively expensive.
Furthermore, from German utility model 79 19 142 a thin layer measuring resistor is known for temperature measurements in which a ceramic platelet is provided as a carrier with a thin platinum coating as a resistance layer, wherein the resistance layer has electrically connected lead wires. The thin layer measuring resistor is arranged in a ceramic housing which consists of two halves; wherein the halves are fused or glued together at their interface with a binding agent, and the connecting wires leading outward from the measuring resistor are embedded in the binding agent. Owing to the two-shell housing, a comparatively precise construction is necessary.
An object of the invention is to create a comparatively simple to produce temperature sensor which can be manufactured economically and can be installed in durable consumer goods, as for example, washing machines, dryers, and temperature regulators in motor vehicles.
The object is accomplished in that a casing serves as a primary housing which together with the embedded measuring resistor is surrounded by an additional plastic extrusion coating as an outer housing, wherein the leads are passed to the outside through the plastic extrusion coating.
The simple, robust construction proves especially advantageous for optimal sealing against the surrounding atmosphere, so that the sensor can also be used in an aggressive environment. In addition to this, it can be economically produced.